The long term goal of this research project will be an investigation of the possible relationship of heme oxygenase activity, the proposed rate limiting enzyme in heme degradation, to the cellular heme content under both physiologic and pathologic situations. The maintenance of hepatic heme levels thus may be under control of heme oxygenase as well as ALAS and consequently, the content of many heme proteins whose synthesis and degradation is regulated by heme may also be affected by the activity of these enzymes. The consequences to the cell of a decrease in cellular heme as a result of an increase in heme oxygenase might be manifested as a lowered ability of microsomal cytochrome P-450 to metabolize drugs. In addition, the activity of hepatic heme oxygenase if influenced by various hormonal states, heavy metals such as iron or a combination of iron with chemicals which cause experimental porphyria. The applicant plans to study the activity of heme oxygenase in a control animal and its response to various factors which cause and induction of this enzyme. In particular we will be investigating the effect of alcohol, iron, and certain steroid hormones, benzene and other environmental agents on the synthesis and degradation of heme particularly as they relate to induction of heme oxygenase activity. In addition, we plan to continue purification of heme oxygenase so that antibodies can be made allowing for an immune enzyme assay. The immunoprecipitation technique for enzyme activity may provide a very sensitive means to measure heme catabolism and permit an investigation at the transcriptional or the translational level of the mechanism of its induction in different human diseases. the applicant plans to continue and extend study of regulation of porphyrin and heme metabolism in erythyroid cells. More specifically, we plan to investigate the role of heme on the controlling heme enzymes and how this in turn effects total cell function, maturation and differentiation. In particular, we will be investigating the effect of various environmental agents and iron on the morphological and biochemical changes in bone marrow and on in vitro development of erythroid colonies. These colonies will serve a model system for elucidating basic molecular mechanism of hemoglobin synthesis as well as the mechanism of production of anemia.